Union in the C language

1. Multiple members can be defined in union, and the size of the Union is determined by the size of the largest member.
2. Union members share memory of the same block size, only one member can be used at a time, in stark contrast to the struct.
3. Assigning a value to a member overrides the values of other members (not surprisingly, because they share a piece of memory.) but only if the member has the same number of bytes, when the number of bytes of the member does not only overwrite the value on the corresponding byte, such as assigning a value to a char member will not overwrite the entire int member, because Char occupies only one byte and int is four bytes.

4. The order in which the Union union is stored is that all the members are stored from the low address.
Let's look at a simple code:

#include <sctdio.h>typedef union{CharC; intA; intb;} Demo;intMainintargcChar**argv)        {Demo D; D.C='a'; D.A=Ten; D.B= A; printf ("Size:%d\n",sizeof(d));//printf ("%d\n", D.C);printf"%c\t%d\t%d\n", D.C, D.A, D.B); return 0;}

Resources:

Http://www.programlife.net/union-struct-in-c.html

http://blog.csdn.net/huqinwei987/article/details/23597091

Union in the C language